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late notice

Boston College
Department of Physics

Nernst Effect and In-Plane Vortex-Like Excitations in Pseudogap Region of Cuprate Superconductors

Professor Hai-Hu Wen
National Lab for Superconductivity, Institute of Physics, Chinese Academy of Sciences
Beijing, China

Nernst effect has been measured for an underdoped and an optimally doped La2-xSrxCuO4 single crystal with the magnetic field applied along different directions. For both samples, when H || c, a significant in-plane Nernst voltage appears above Tc and keeps measurable up to a high temperature ( 100 K ) as reported earlier [ Nature 406, 486(2000) ]. However, when H || a-b plane the Nernst signal along c-axis drops below the noise level quickly above Tc for the underdoped sample. This may suggest that the superconducting condensation is established simultaneously with the Josephson coupling ( or the coherent motion of Cooper pairs ) along c-axis. Moreover, the in-plane Nernst data with field at different angles shows a nice scaling behavior with the c-axis component of the field. All these give strong indications for strictly in-plane vortex-like excitations in the pseudo-gap region.
Thursday, November 6, 2003
4:00 p.m.
Seminar Room